Detonation shock tubes



July l2, 1966 M. R. .lcHNsoN DETONATION SHOCK TUBES 4 Sheets-Sheet 1 Filed Dec. 20, 1962 July l2, 1966 M. R. JOHNSON DETONATION SHOCK TUBES 4 Sheets-Sheet` 5 Filed Dec. 20, 1962 VSP# IN VENTOR.

M/LTON R. JOHNSON ATTYS.

DETONATION SHOCK TUBES Filed Dec. 2o, 1962 4 sheets-sheet 4 FIG.5

INVENTOR.

M/L TON l?. JOHNSON United States Patent O 3,260,103 DETONATION SHOCK TUBES Milton R. Johnson, Chicago, Ill., assignor to General American Transportation Corporation, Chicago, Ill., a corporation of New York Filed Dec. 20, 1962, Ser. No. 246,111 18 Claims. (Cl. 73-12) The present invention relates to detonation shock tubes, and more particularly to such shock tubes capable of generating high overpressure shock or blast waves in air, wherein the overpressures mentioned are at least 100 p.s.i.

It is a general object of the invention to provide a shock tube of improved construction and arrangement that is productive of blast waves in air simulating blast waves produced in air by high explosions extending from the kiloton range through the megaton range (in terms of equivalent tons of T.N.T.).

Another object of the invention is to provide a detonation shock tube that is recoilless.

Another object of the invention is to provide a shock tube comprising a first chamber containing a detonable gas mixture, a cooperating second chamber containing air, a frangible partition separating the front of the first chamber from the rear .of the second chamber, and facility for initiating a detOnation wave in the gas mixture in the extreme rear end of the first chamber, whereby the detonation wave has a substantial overpressure and travels forwardly at supersonic Velocity in the gas mixture and through the first chamber so that the detonation wave ruptures the frangible partition and sets up a shock or blast wave in the air in the extreme rear end of the second chamber, and whereby the shock or blast wave has a substantial overpressure and travels forwardly at supersonic velocity in the air and through the second chamber.

Another object of the invention is to provide in a detotube of the character described, and further comprising a frangible diaphragm initially closing the rear end of the rst chamber, whereby the diaphragm is ruptured substantially simultaneously with the initiation of the detonation wave in the extreme rear end of the first chamber, thereby to prevent the presence of a rearwardly traveling detonation wave in the first chamber and the consequent production of recoil forces upon the rear end -of the shock tube.

A further object of the invention is to provide a shock tube of the character described, wherein the Walls of the shock tube are formed essentially of metal of relatively thin gauge, since the detonation Wave that is produced in the first chamber is not productive of substantial rupturing stresses in the walls dening the first chamber, notwithstanding the overpressure of the detonation wave moving forwardly at supersonic velocity through the gas mixture in the first chamber.

Another object of the invention is to provide in a detonation shock tube, yan improved detonable gas mixture of consisting essentially of propane and oxygen.

Another object of the invention is to provide a detonation shock tube, an improved detonable gas mixture of C3H8 and O2, wherein an advantageous range of the ratio O2/C3H8 is employed for the purpose of maximizing the detonation velocity of the detonation wave produced in the shock tube.

Another object of the invention is to provide in conjunction with a detonation shock tube, an improved system `for charging a detonable gas mixture into the shock tube and for purging gaseous detonation products fromv the shock tube.

Another object of the invention is to provide a detonation shock tube that comprises a plurality of stationary sections and a plurality of removable sections, thereby to facilitate simple and rapid utilization of the shock tube in producing successive tests therewith.

Another object of the invention is to provide a detonation shock tube of the character described, and further comprising a simple mechanism for moving each of the movable sections of the shock tube between its assembled and disassembled positions with respect to the adjacent stationary sections of the shock tube, thereby greatly to facilitate inspection, cleaning and repair of the shock tube.

Another object of the invention is to provide a detonation shock tube of the character described, wherein each of the mechanisms mentioned essentially comprises a rack and gear mechanism, so as to preserve the angular relationship of fit in the assembled position of the movable section when the same is moved into its disassembled position.

A further object of the invention is to provide in a shock tube, in which there is produced a blast wave in air and having a high Ioverpressure and traveling therethrough at supersonic velocity, a test section disposed in an intermediate portion of the shock tube with respect to the opposite ends thereof, wherein the test section comprises both a first facility for accommodating the release of a first portion of the blast wave from the test section for external test purposes and a second facility for accommodating the release of a second portion of the blast wave from the test section for the purpose of substantially counterbalancing unbalancing forces induced in the test section by the release of the first portion of the blast wave.

A further object of the invention is to provide in a shock tube, including a test section of the character described, an exceedingly simple mechanism arranged in the test section for producing the release of the two portions of the shock wave mentioned under conditions such that two substantially equal and opposite forces are produced in the test section that are substantially cancelled therein, thereby to prevent any substantial unbalancing forces from being exerted upon the adjacent sections of the shock tube.

A still further object of the invention is to provide a detonation shock tube of the character described, vthat is substantially recoilless and that is subject to no substantial unbalancing forces, whereby the shock tube may be readily mounted upon the earth, as a support, without the provision of elaborate footings, foundations, recoil abutments, counterweights, and like structures, that have been heretofore necessary in the mounting arrangements of such shock tubes.

Further features of the invention pertain to the particular arrangement of the elements of the shock tube, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a fragmentary schematic diagram of a detonation shock tube -and control system therefor embodying the present invention;

FIG. 2 lis a graphic representation of certain performance characteris-tics of the shock tube;

FIG. 3 is la graphic representation of other performance characteristics of the shock tube;

FIG. 4 is a fragmentary plan view of the shock tube;

FIG. 5 is an enlarged side elevational View, partly in section, of the test section of the shock tube, this view being taken in the direction :of the iarnows along the line 5-5 in FIG. 4;

FIG. `6 is another enlarged side elevational view of the test section, similar to FIG. 5, -but with certain parts broken away and with other parts in section, and illustrating certain mechanism incorporated within the test section;

FIG. 7 is an enlarged vertical sectional view of the test section, this view being taken in the direction of the arrows along the line 7--7 in FIG. 6;

FIG. 8 fis another enlarged vertical sectional view of the test section, this view being taken in the direction of the arrows along the line 8-8 in FIG. 6.

Referring now to FIG. 1 of the drawings, there are illustrated a detonation shock tube 10, and control system therefor, embodying the features of the present invention. The shock tube 10 essentially comprises an elongated tubular casing 111 that is divided into a number of casing sections, as explained more fully hereinafter, for purposes of ready construction and manipulation; the intermediate portion of the casing 11 carries a frangible partition 12 that initially divides the same into an elongated rear chamber 13 and lan elongated front chamber 14; the extreme rear end of the casing 11 is initially closed by a frangible diaphragm 15; and the extreme front end of the casing 11 is open to the atmosphere. The casing 11 is preferably formed of steel; and the partition 12 and the diaphragmy 15 may be formed of any suitable frangible materials, such as, light-gauge sheet metal, plastic sheet material, etc. The rear chamber 113 defined in the rear end of the casing 11 between the diaphragm 15 and the partition 12 constitutes a detonation chamber; while the front chamber 14 defined in the front end of the casing 11 between the partition 12 and the open front end of the casing 11 constitutes an air chamber. The intermediate portion of the front end of the casing 11 carries a test casing sec-tion TS disposed well forwardly of the partition 12 and well rearwardly of the open front end of the casing 11.

The test casing section TS has a bottom test opening 17 formed therein for the purpose of exposing to a blast wave a specimen undergoing test; and in order to facilitate the .test a container 18 is arranged directly below the test opening 17. The container 1S is entirely disconnected from the test casing section TS and is supported below the test opening 17 in any suitable manner, such, for example, as by the earth 4disposed below `the test casing section TS, as indicated at 19; the container 18 has an open top that communicates directly with the bottom interior portion of the test casing section TS; and the container 18 is illed with the specimen that is to be tested, as indicated at 20. The specimen 20 that is most frequently subjected to such blast test is earth or soil itself; whereby it may be assumed that the specimen 20 comprises a soil sample. Also, the test casing section TS has atop diversion opening 21 therein that is generally positioned above the bottom test opening 17 and that is partially closed by a cooperating block 22 rigidly secured in place in the upper portion of the test casing section TS to the adjacent wall structure. The block 22 is preferably formed of steel and includes a flat bottom surface 22b positioned substantially in a horizontal plane, an upwardly and forwardly inclined at top surface 22t disposed at a slight angle tothe bottom surface 22h, and a sharp rear edge 22e disposed at the junction between the two surfaces 22b and 22t. The angle mentioned may be of the order of about 10 and the block 22 is arranged with the rear edge 22e thereof disposed rearwardly of the front base 22 thereof, and so that the rear edge 22e thereof is positioned adjacent to and below the rear edge of the top opening 21 and the front base 22 thereof lis positioned forwardly of the front edge of the top opening 21. Accordingly a throat opening 23 is defined between the rear edge 22e of the block 22 and the upper portion of the test casing section TS at the rear edge of the top opening 21; which throat opening 23 extends forwardly and upwardly over the top surface 22t of the block 22 and through the test opening 17 and to the exterior and communicating with the atmosphere; which throat opening 23, top opening 21 and block 22 are constructed 'and arranged to cause a strong standing shock wave, indicated at 24 to be attached to the rear edge 22e of the block 22 and to extend through the top opening 21 .to the atmosphere under -certain operating conditions, as explained more fully hereinafter.

Finally, the central portion of the inner face of the diaphragm |15 carries a detonator 25, of any suitable type, disposed in the extreme rear portion of the detonation chamber 13. More particularly, the detonator 25 may be of .the electrically triggered type, so that the same may be readily detonated from the exterior of the shock tube 10 by an operator upon closure of an electric operating circuit therefor, not shown. Specifically, the detonator 25 may essentially comprise a typical dynamite cap of the mercury fulminate type provided with an electrical ignition heater filament, all of conventional construction and arrangement.

Turning noiw to the control system that is operatively associated 'with the sho-ck tube 110, -there is provided an arrangement for evacuating air yfrom the detonation chamber 13 that essentially compri-ses a vacuum pump 31 driven by -an associated electric drive motor 32. The vacuum pump 31 comprises an inlet connected by a header 313 to the rear portion of the casing 1:1 and communicating with fthe detonation chamber 13 and an outlet connected by a pipe 34 to the atmosphere, the header 313 including a manually operable shut-off valve 35. Also, a detonable gas mixture supply arrangement is provided for the `shocl tube 10 that includes la tube or tank 4-1 containing gase- -ous oxygen under substantial gauge pressure, a tube or tank 42 containing liquefied propane under substantial gauge pressure, and a manifold 1423i. The manifold t6 is connected to the rear portion of the casing 111 and comlmunicating with the detonation chamber `13, .and includes a manually `operable Ishut-off valve 44. The two tubes yt1 and `42 are respectively selectively connectible to the manifold 43 by two respectively -associated throttling valves 45 and 46. Further, a purge Iarrangement is provided ifor the shock tube l1i) that inclu-des a Iheader 511 connected to the rear portion -of the casing 11 and communicating with the detonation chamber 113, the header 51 including a manually operable shut-off valve 52. Flurther, the purge arrangement includes an air filter 53 that is provided with air inlet structure 54, .and that communicates with the inlet of a :blower 55. The outlet of the blower 55 communicates with the inlet of an air washer 56; the outlet of the air washer 56 communicates with 'the inlet of a water deentrainer 57; and the outlet of the 'water deentrainer 57 communicates lwith the inlet of another blower 58. The outlet of the blower 53 is connected to -theinlet of a dryer 59; the outlet of the dryer I59 is connected to the inlet of a primary vheater 6i); and the outlet of the primary beater 65 is 4connected to the inlet of .a compres-sor 61 that is driven by an electric -drive motor 62. The outlet of the compressor 61 is connected to the inlet of a secondary heater 63; and the outlet of the `secondary beater 63 is connected to the header y51. T-he dryer 59 and the primary heater 6i) respectively ho-use the evaporator `64 and the condenser 65 ot a refrigerating machine, also including a compressor 66 driven by an electric drive motor 67. The outlet of the compres` sor 66 is connected to the inlet of the condenser 65; the

outlet of the condenser 65 is connec-ted by an expansion valve 68 to the inlet of the evaporator 64; and the outlet of the evaporator 64 is connected to the inlet of the compressor 66. The refrigerating machine also contains a charge of refrigerant, such as 1F12, and the .secondary heater 63 contains a suitable .heating unit, such as a steam coil 69.

)Considering now the general mode of operation ofthe shock tube and the associated control system therefor,

it may be assumed that the detonation chamber 13 con- -tains a charge of detona-ble gas (for example, a mixture of propane and oxygen, .as explained more fully hereiniafter), that the air chamber 14 contains air at atmospheric pressure, that a test specimen (for example, a 4soil sample) is arranged in the container 18 and is in readiness for the test. Also, it may be assumed that the shut-off valves 52, 44 and 35 occupy their closed positions, that the throttling valves 45 and 46 occupy their closed positions, that the detonator is in readiness to be ignited, and that all of the required instrumentation is in ready con-dition. On the count-down and at time 0, the operator closes the electric circuit, not shown, to the Idetonator 2S so `as to effect detonation thereof, |with the result that the -detonable gas contained in the detonation chamber 113 is instantaneously detonated immediately yadjacent to the front 'face of the diaphragm 15. Of course the -detonation immediately ruptures the lig-ht diaphragm 15 `and places the extreme `rear end of the casing :11 Iinto communication with the atmosphere, so `as 'to prevent recoil :forces upon the casing 11. Also, the 'detonation produces a detonation wave lhaving a front that is at high -overpressure and that moves forwardly at -supersonic Velocity through the detonable gas mixture in Ithe detonation chamber 13. After the required exceedingly short time interval, the detonation wave moves forwardly to the extreme front end of the detonation c-hamber 13, shatters the partition 12, and produces a blast wave in the air in :the extreme rear end of the fair chamber 14. Of course, the -blast 'wave has a front that is Iat high overpre-ssure Iand that moves forwardly at supersonic velocity through the air in the air chamber 14. After the required exceedingly short time interval, the front of the blast wave moves into the test casing section TS; whereby the blast ywave passing `over the bottom test opening -17, :subjects the soil sample 20 in the container 118 to the high pressure, high temperature, high :impact and other characteristics of such a lshock :wave for the test purpose, in a known manner. Since the bottom test opening 117 constitutes a hole 'in the test casing section TS, upwardly directed unba-lancing forces are exerted :by the front of `the blast wave upon the bottom surface 2`2b of the :block 22 -that tend lto lift or blast the test casing section TS from its support and upwardly into the atmosphere. However, these upwardly directed unbalancing forces mentioned are counterbalanced by downwardly directed forces that are exerted upon the top surface 221i of the block 22 by virtue of the production of the strong standing shook wave, 'indicated at 2'4, that is also produced in the test casing section TS incident to the passage of the front of the blast wave therethrough. yMore particularly, as the blast 'wave front moves forwardly through the test casing section TS the high pressure air is pumped or forced from the top portion thereof through the throat opening 23 and over the top surface 22t of the 4block 22 and through the top opening 21 to the atmosp-here; which movement `at supersonic velocity of air through the throat opening 23 cau-se the strong standing `shock Iwave 24 to attach itself to the edge 22e of the block 22 and to extend upwardly and forwardly through the top opening 21 into the atmosphere, .a well-known phenomenon .in aerodyamics; whereby a high pressure yarea is produced forwardly and below the standing shook Wave 24 in the usual manner, `so that the top surface 221 of the block 22 is subjected to this high pressure in order to produce a corresponding downwardly directed force upon the block 22 that substantially matches and counterbalances the previously mentioned upwardly directed unbalancing :force that is exerted upon the blo-ok 22.

In the present example, the `desired downwardly directed force is produced upon the top surface 2-2t of the block 22 when the angle between the two surfaces 22b and 22t lof the block 22 is approximately 10.

Thus, the passage of the blast wave through the test casting section TS is productive of no substantial unbalancing forces thereupon, so that the position of the test casing section TS upon its mounting or foundation is not disturbed; and thus not substantial stresses are transmitted from the test casing section TS to the adjacent sections or portions of the casing 11.

After passing t-hrough the air in the test casing section TS the blast wave front proceeds forwardly through the air in the front portion of the casing 11 and through the open front end thereof into the atmosphere.

Of course, a low-pressure part follows the high-pressure part of the detonation wave in the detonation chamber 13, and a low-pressure part follows the high-pressure part of the blast wave in the air chamber 14, in a manner well understood in aerodynamics, 'but these phenomena are not here developed, as they are not of prime or fundamental importance in the testing of effects produced by blast waves generated by high explosions. Accordingly, the simulated effects of the low pressure part of the blast wave is not of prime or fundamental importance, and the description thereof herein is omitted in the interest of brevity.

Such detonation of the propane-oxygen mixture in the detonation chamber 13 is productive of such gaseous detonation products as H2O vapor, CO2, CO, etc.; whereby it is necessary to purge these gaseous products from the shock tube 10 following a shot thereof. In order to accomplish this end, the purging arrangement is operated, and the shut-off valve 52 is opened. Air is taken into the air inlet 54 from the atmosphere, and ltered in the air filter 53, and washed in the air washer 56 and then subjected to water deentrainment in the deentrainer 57; whereby the air supplied to the blower 58 is clean, but substantially saturated with moisture at the ambient temperature. In the dryer 59 the temperature of the air is substantially reduced, so that substantial moisture is extracted therefrom both by the dewpoint action and by the freezing-out action of the evaporator 64. In the primary heater 60 the temperature of the air is elevated slightly higher than the ambient temperature, since the re-frigerating machine is operating as a heat-pump. However, the relative humidity of the air supplied to the compressor 61 may be as low as about 10%. The air is further heated by the action of the compressor 61 and is still further heated by the secondary hearter 63, since live steam is normally conducted through the steam coil 69 housed in the secondary heater 63; whereby the air supplied to the header 51 is not only quite hot, having a temperature normally in the general range -200 F., but the same is exceedingly dry, having a relative humidity as low as about 1%.

The blast of hot dry air from the header 51 is injected into the rear end of the casing 11 and proceeds both rearwardly and forwardly in the casing 11, absorbing water vapor and sweeping therewith CO2, CO, etc., from the casing 411. After the extreme rear end of the casing 11 has been thoroughly swept, the ruptured diaphragm 15 is replaced with a new diaphragm 15 in order to close the extreme rear end of the casing 11; whereby the entire hot dry air blast from the header 51 proceeds forwardly through the casing 11. A minor portion of the forwardly moving gases escapes through the openings 17, 213 and 21 in the test casing section TS, but the major portion of these gases is swept forwardly from the open front end of the casing 11.

The purging arrangement is very advantageous as the same causes substantially all of the detonation products to be quickly removed from the casing 11, lto be transported from the area or site of the shock tube that is occupied by personnel, and prevents the deleterious effects of moisture in the casing 11.

After the purging operation has been carried out in a satisfactory manner, the shut-off valve 52 is closed, and the operation of the purging apparatus is arrested. Then the ruptured partition 12 is replaced with a new partition 12; whereby the casing 11 is again divided into the rear chamber 13 and the front chamber 14, both containing principally air. The shut-off valve 35 is then opened, and operation of the vacuum pump 31 is initiated. The vacuum pump 31 removes the great proportion of the air from the closed detonation chamber by the reduction of the pressure therein into the general area of -1 mm. Hg; whereby the shut-off valve 35 is closed and operation of the vacuum pump 31 is arrested.

At this time another charge of propane-oxygen mixture is introduced into the detonation chamber 13; and to 4accomplish this the shut-off valve 44 is opened, and ordinarily the throttling valve 45 is rst opened to admit oxygen from the tube 41 into the manifold 43, from which it readily flows into the detonation chamber 13. After the required admission of oxygen into the detonation cham-ber 113, as indicated by the pressure therein, the throttling valve 45 is closed and the throttling valve `46 is opened. Propane from the tube 42 ows into the manifold 43 and thence into the detonation chamber 13. After the required admission of propane into the detonation chamber 113, as indicated by the total pressure therein, the throttling valve 46 is closed; and then the shut-off valve 44 is closed. At this time, the detonation chamber 13 contains another propane-oxygen charge, and the shock tube 10 is fundamentally ready for the next shot in the manner describedabove.

At this point it is noted that any required proportionation of O2 and C3H8 at any required final pressure of the mixture may be readily obtained in the detonat-io-n chamber by rst introducing the required O2 to produce an initial predetermined pressure and then -by introducing the required C3H8 to produce the desired nal pressure, since this is a simple two-part gas system and the final pressure is necessarily produced by the two partial pressures of .the two gases involved in the mixture. Thus, a chemist may readily calculate the initial pressure that will be produced in the detonation chamber 13 by the desired fraction of O2 in the final O2-C3H8 lmixture. Thus, the plan suggested above involving the introduction of O2 to obtain a desired initial pressure, followed by the introduction of C3H8 to obt-ain a desired final pressure, automatically produces -a fixed O2/C3H8 ratio in the mixture, as explained above, and thus greatly simplifies the operation and the control of the shock tube 19, as explained more f-ully hereinafter.

Considering now in some particularity the O2-C3H8 detonation system, Iit is pointed out, in connection with FIG. 2, that the peak detonating pressure in p.s.i.a. in the detonation chamber 13 is substantially functional both upon the O2/C3H8 ratio of the detonable charge of mixed gases employed and upon the initial pressure in p.s.i.a. utilized. The data for the curves p1, p2 and p3 in FIG. 2 was derived utilizing the respective initial pressures of 14.7 p.s.i.a., 29.8 p.s.i.a. and 58.8 p.s.i.a.; and it will be observed that the peak detonating pressure 4in p.s.i.a in the detonating chamber 13 is more or less directly proportional to the initial pressure in p.s.i.a.; whereas, in each case, the peak detonating pressure in p.s.i.a. is more or less maximized at -a ratio of O2/C3H8 in the rather narrow band 3 to 5. Also, it is pointed out, in connection with FIG. 3, that the detonation velocity in ft./sec. in the detonation chamber 13 is substantially functional upon the O2/C3H8 ratio of the detonable charge of mixed gases employed and slightly functional upon the initial pressure in p.s.i.a. utilized. The data for the curves p1, p2 and p3 in FIG. 3 was derived utilizing the corresponding initial pressures, as previously mentioned; and it will be observed that the peak detonation velocity in ft./sec. in the detonating chamber 13 increases slightly with increasing initial pressure in p.s.i.a.; whereas, in each case, the detonation velocity in ft./sec. is more or less maximized at .a ratio of O2/C3H8 in the rather nariow band 2.5 to 3.5. Hence, for both a maximumv peak detonating pressure and a maximum detonation velocity in the detonating chamber, in the example disclosed, the ratio of O2/C3H3 should be abo-ut 3. Of course, both of the characteristics are increased with increasing initial pressure. For example, with the initial pressure of 58.8 p.s.i.a. and with the O2/C3H8 ratio of 3, the peak detonating pressure is approximately 1400 p.s.i.a., and the detonation velocity is approximately 8,350 ft./sec., as respectively illustrated by the curve p3 in FIG. 2 and by the curve p3 in FIG. 3.

The blast wave that is produced in the air in the front chamber 14 of the shock tube 10 has an overpressure that is only somewhat below that of the overpressure of the detonation wave that is produced Ain the detonation chamber 13 of the shock tube 10, in the example. Accordingly, high overpressure shock waves in air can be produced without exerting undue explosive stresses in the driving or detonation chamber 13 of the shock tube 10.

Turning now to FIGS. 4 to 8, inclusive, some structural details of the shock tube 10 are illustrated; whereby the casing 11 may comprise the components 11a, 11b1 or 11b2, 11C, TS1 or TS2 and 11d. Specifically, the rearmost casing section 11a terminates in a `ring 101 that cooperates with a ring 182 and between which the periphery of the diaphragm 15 is clamped in place. Of course, the ring 1112 is removably secured to the ring 101, as by an annular series of bolts, not shown, so las to accommodate ready replacement of the frangible diaphragm 15 following rupture thereof incident to operation of the shock t-ube 10 in the manner previously explained. Two of the `casing sections 11b1 and 11112 are provided, as a matter of convenience, so that one of the casing sections 11b1 may be in the assembly of .the casing 11, while the other of the casing sections 11b2 is undergoing preparation for reuse. The two casing sections 11b1 and 11b2 are identical, and ea-ch thereof carries one of the frangible partitions 12. Specifically, the casing .section 11b1 comprises two identical parts 111 and 121; the part 111 including the pair of left-hand rings 112 and 113 -arranged in longitudinally `spaced-apart relation and the right-hand ring 114; and the part 121 including th-e pair of right-hand rin-gs 122 and 123 arranged in longitudinally spaced-apart relation and the left-hand ring 124. The two rings 114 and 124 are suitably removably secured together, as by an annular series of bolts, not shown, with the frangible partition 12 securely clamped in place therebetween; and the two rings 112 and 122 are respectively suitably removably secured to two rings 103 and 104 respectively carried by the adjacent casing sections 11a and 11e, as by two annular series of bolts, not shown.

A ring gear 115 is rigidly secured in place between the rings 112 and 113 to the part 111; a ring `gear 125 is rigidly secured in place between the rings 122 and 123 to the part 121; and the two ring gears 115 and 125 are respectively supported by two laterally extending and longitudinally spaced-apart racks 116 and 126 that are respectively carried by two concrete footings 117 and 127 respectively securely anchored in place in the earth, as indicated at 10S.

Thus, the casing sections 11b1 and 11b2 are selectively movable between -operative and repair positions, as re-,

spectively illustrated by the positions of the casing sections 11b1 and 11192, along the racks 116 and 126i, thereby to facilitate ready replacement of the ruptured partitions 12 in the normal use of the shock tube 10 in the manner previously explained. The arrangement is very advantageous, since the cooperation between the ring gears 115, and the racks 116, 126 preserves the angular positions 4of fit of the casing sections 11b1, 11b2, notwithstanding lateral rolling of the casing sections 11b1 and 11b2 into their repair positions. ln other words, when one of the Casin-g sections 11b1 or 11b2 is rolledinto its operative position with respect to the adjacent ends of the casing sections 11a and 11C, the bolts, not shown, may be irnmediately placed in the co-operating rings 103, 112 and 104, 122 for the reason noted above.

The test casing section TS1, as illustrated in FIGS. 4 to 8, inclusive, is the same as that previously described in conjunction with the shock tube 10, as illustrated in FIG. 1; whereas the test casing section TS2 is of modified construction, as explained below.

Specifically, the test casing section TS1 comprises the substantially cylindrical wall 11 having the bottom test opening 17 formed therein and the top diversion opening 21 formed therein and carrying the substantially wedge-shaped block 22, all as previously described in conjunction with FIG. l. Further, the wall carries the left-hand pair of rings 131, 132, with a ring gear 133 therebetween, and the right-hand pair of rings 134, 135, with a ring gear 136 therebetween; which ring gears 133 and 136 respec-tively cooperate with two laterally extending and longitudinally spaced-apart racks 137 land 138 respectively carried by two concrete rfootings 139 and 140 supported by the earth, as indicated at 105. Thus, the test casing section TS1 is selectively rollable between operative and inspection positions by cooperation between the ring gears 133, 136 and the racks 137, 138, in a manner as explained in conjunction with the casing sections 11b1 and 11b2. Thus, the arrangement preserves the angular positions of fit between the rings 131, 134 and the rings 106 4and 107 respectively carried by the adjacent ends of the casing sections 11C and 11d; and further, the arrangement positively insures respective top and bottom positioning of the top and bottom openings 21 and 17, respectively, when the test casing section TS1 -occupies its operative position, as shown in FIGS. 4 and 5. Hence, when the test casing section TS1 occupies its operative position, as shown in FIG. 5, the bottom opening 17 is positioned immediately above the open top `of the container 18 in which there is -arranged the soil sample 20 that is to be tested, the container 18 being supported in a hole provided in the earth, as indicated at 105. The cylindrical wall 11 is reinforced adjacent to the rear en-d of the bottom opening 17 by a surrounding ring 141 and adjacent to the front end of the top opening 21 by a surrounding ring 142. The wall 11 is reinforced adjacent to the rear end of the top opening 21 by two adjacent partial rings 143 and 144; and the wall 11 is reinforced adjacent to the front end of the bottom opening 17 by a partial ring 145. The wall 11 is reinforced adjacent to the opposite sides of the top opening 21 by a pair of side strips 146; and the wall 11 is reinforced adjacent tothe opposite sides of the bottom opening 17 by a pair of side strips 147. In the arrangement, the reinforcing elements 141, 142, 143, 144, 145, 146 and 147 may be suitably welded to the adjacent wall 11, thereby to provide the test casing section TS1 of strong rigid construction.

The construction of the test casing section TS2 is basically the same as that of the above described test casing section TS1, except that the cylindrical wall 11 of the test casing section TS1 is imperforate, thereby eliminating the special reinforcing elements that are incorporated in the test casing section TS1. Thus, the test casing section TS2 comprises the elements 11', 131', 132', 133', 134', 135' and 136' respectively corresponding to the elements 11, 131, 132, 133, 134, 135 and 136 incorporated in the test casing section TS1. Of course, the test casing section TS2 is employed in the shock tube when it is desired entirely to contain the test specimen in an obvious manner.

In View of the foregoing, it is apparent that there has been provided a recoillness detonation shock tube. Also,

the shock tube comprises an improved control system therefor rendering it possible to conduct shock tests in rapid succession. Further, the construction and arrangement of the shock tube is of improved and simplified character, thereby accommodating the conduction of shock tests from the shock tube to the exterior, Without the' necessity of heavy counterbalancing structure, and

without the necessity of heavy recoil abu-tments. Also, an improved detonable gas mixture and arrangement are provided for operating the shock tube, wherein the ratio of the driving pressure of the detonation chamber in relation to the overpressure of the shock wave in air is close to unity, thus minimizing the strength requirements of lthe shock tube. Specifically, the gas mixture mentioned essentially comprises propane and oxygen and involves an important range of ratios of O2/C3H8 in the gas mixture and an important initial pressure range of the gas mixture in the detonating chamber of the shock tube.

While there has been provided what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications that fall within the true spirit land scope of the invention.

What is claimed is:

1. A shock tube comprising an elongated tubular casing, a frangible partition carried by an intermediate portion of said casing and initially dividing said casing into rear and front chambers, said front chamber containing air, .a frangible diaphragm carried by the rear end of said casing and initially closing the rear end of said rear chamber, means for supplying a detonable ygas into said rear chamber, means for initiating detonation vof the gas immediately :adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the g-as to place the rear end of said rear chamber into communication with the atmosphere in order to prevent substantial recoil forces upon said casing, whereby la detonation wave is initiated in the gas in the rear end of said rear chamber, said detonation wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the gas in said rear chamber, means responsive to said forwardly traveling detonation wave for subsequently effecting rupture of said partition and lthe consequent production of =a blast w-ave in :the air in the rear end of said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said front chamber, the front e'nd of said front chamber communicating with the atmosphere in order to prevent substantial thrust forces upon said casing, and a tes-t station in said front chamber and subject to said forwardly traveling blast Wave.

2. The shock tube set forth in claim 1, wherein the detonable gas essentially comprises la gaseous combustible substance and a gaseous oxidizing substance.

3. The shock tube set forth in claim 1, wherein the detonable gas essentially comprises a mixturel of propane and oxygen.

4. The shock tube set forth in claim 1, wherein the detonable gas essentially comprises a mixture of oxygen and propane, the molar ratio between O2 and CSHB in the mixture being in the general range 2 to 6.

5. A shock tube comprising an elongated tubular casing, `a frangible partition carried by an intermediate portion of said casing and intially dividing said casing into rear and front chambers, said front chamber containing air, a frangible diaphragm carried by the rear end of said casing and initially closing the rear end of said rear chamber, means for supplying a detonable gas under gauge pressure into said rear chamber, the detonable gas essentially comprising a mixture of oxygen and propane, the molar ratio between O2 and CSHB in the mixture being in the general range 2 to 6, the initial gauge pressure of the mixture in said rear chamber being in the general range 1 to 3 atmospheres, means for initiating detonation of the gas immediately adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the gas to place the rear end of said rear chamber into communication with the atmosphere in order to prevent substantial recoil forces upon sa-id casing, whereby a detonation wave is initiated in the gas in the rear end of said rear chamber, said detonation wave being chara-cterized by a substantial overpressure and forward travel at supersonic velocity through the gas in said rear chamber, means responsive to said forwardly traveling detonation wave for subsequently effecting rupture of said partition and the consequent production of a blast wave in the air in the rear end of said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said front chamber, the front end of said front chamber communicating with the atmosphere in order to prevent substantial thrust forces upon said casing, and a test station in said front chamber and subject to said forwardly traveling blast wave.

6. A shock tube comprising an elongated substantially horizontally disposed tubular casing, an intermediate section of said casing being selectively removable with respect to rear and front sections thereof, said intermediate casing section carrying a replaceable frangible partition, whereby said frangible partition carried by said intermediate casing section when said intermediate casing section is in place between said rear end front casing sections initially divides said casing into rear and front chambers respectively disposed in said rear and front casing sections, said front chamber containing air, a frangible diaphragm carried by the rear end of said rear casing section and initially closing the rear end of said rear chamber, means for supplying a detonable gas into said rear chamber, means for initiating detonation of the gas immediately adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the gas to place the rear end of said rear chamber into communication wit-h the atmosphere in order to prevent substantial recoil forces upon said casing, whereby a detonation wave is initiated in the gas in the rear end of said rear chamber, said detonation wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the gas in said rear chamber, rneans responsive to said forwardly traveling detonation wave for subsequently effecting rupture of said partition and the consequent production of a blast wave in the air in the rear end of said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said front chamber, the front end of said front chamber communicating with the atmosphere in order to prevent substantial thrust forces upon said casing, and a test station in said front chamber and subject to said forwardly traveling blast Wave.

7. The shock tube set forth in claim 6, and further comprising mechanism for selectively moving said intermediate casing section laterally between an operative position placed between the respectively adjacent ends of said rear and front casing sections and a repair position displaced from between the respectively adjacent ends of said rear and front casing sections, said mechanism being operative to roll said intermediate casing section between said operative and repair positions and to preserve the locations of longitudinal and circumferential t of said intermediate casing section with respect to the adjacent ends of said rear and front casing sections when said intermediate casing section is returned into said operative position.

8. The shock tube set forth in claim 7, wherein said mechanism essentially comprises a pair of substantially 'i2 parallel longitudinally spaced-apart gears respectively carried by said intermediate casing section, and a pair of substantially parallel longitudinally spaced-apart and laterally extending racks supported externally of said intermediate casing section and respectively engaging said gears.

9. A shock tube comprising an elongated tubular casing, a frangible partition carried by the intermediate portion of said casing and initially dividing said casing into rear and front chambers, said front chamber containing air, a fixture removably carried by the rear end of said casing, said fixture carrying a replaceable frangible diaphragm, whereby said diaphragm carried by said fixture when said diaphragm is in place upon the rear end of said casing initially closes the rear end of said rear chamber, means for supplying a detonable gas into said rear chamber, a detonator carried by t-he front side of said diaphragm and operative to initiate detonation of the gas immediately adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the gas to place the rear end of said rear chamber into communication with the atmosphere in order to prevent substantial recoil forces upon said casing, whereby a detonation wave is initiated in the gas in the rear end of said rear chamber, said detonation wave being characterized by 'a substantial overpressure and forward travel at supersonic velocity through the gas in said rear chamber, means responsive to said forwardly traveling detonation Wave for subsequently effecting rupture of said partition and the consequent production of a blast wave in the air in the rear end of said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said front chamber, the front end of said front chamber communicating with the atmosphere in order to prevent substantial thrust forces upon said casing, and a test station in said front chamber and subject to said forwardly traveling blast wave.

10. A shock tube comprising an elongated tubular casing, a frangible partition carried by the intermediate portion of said casing and initially dividing said casing into rear and front chambers, said front chamber containing air, a frangible diaphragm carried by the rear end of said casing and initially lclosing the rear end of said rear chamber, means for initially evacuating air from said rear chamber, means for supplying a detonable gas into said evacuated -rear chamber, means for initiating detonation of the gas immediately `adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the gas to place the rear end of said rear chamber into communication with the atmosphere in order to prevent substantial recoil forces upon said casing, whereby a detonation wave is initiated in the gas in the rear end of said rear chamber, saidl detonation wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the gas in said rear ch-amber, means responsive to said forwardly traveling detonation wave for subsequently effecting rupture of said partition and the consequent production of a blast Wave in the air in the rear end Iof said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said front chamber, the front end of said front chamber communica-ting with the atmosphere in order to prevent substantial thrust forces upon said casing, a test station in said front chamber and subject to said forwardly traveling blast wave, and means for subsequently supplying air into said casing so as to purge therefrom gaseous detonation products.

11. A shock tube comprising an elongated tubular casing, a frangible partition carried by the intermediate portion of said casing and initially dividing said casing into rear and front chambers, said first chamber con- 13 'taining air, a frangible diaphragm carried by the rear end of said casing and initially closing the rear end of said rear chamber, means -for initially evacuating air from said rear chamber, means for supplying a detonable gas into said evacuated rear chamber, means for initiating detonation of the gas immediately adjacent to and forwardly of said diaphragm so that said diaphragm is substantially instantaneously ruptured by the detonation of the gas to place the rear end of said rear chamber into communication with the atmosphere in order to prevent substantial recoil forces upon said casing, whereby a detonation wave is initiated in the gas in the rear end of said rear chamber, said detonation wave being characterized by a substanti-al overpressure and forward travel at supersonic velocity through `the gas in said rear chamber, means responsive to said forwardly traveling detonation wave for subsequently effecting rupture of said partition and the consequent production of a blast wave in the air in the rear end of said front chamber, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in said fron-t chamber, the front end of said front chamber communicating with the atmosphere in order to prevent substantial thrust forces upon said casing, a test station in said front chamber -and subject to said forwardly traveling blast wave, means for drying and for heating a current of said, and means for subsequently supplying the dry hot current of air into said casing so as to purge therefrom gaseous detonation products.

12. A shock tube comprising an elongated substantially horizontally disposed tubular casing containing air and including rear and intermediate and front sections, means for producing a blast wave in the air in said -rear section, said blast wave being characterized by a substantial overpressure and forward travel at supersonic velocity through the air in successive ones of said rear and intermediate and front casing sections, said intermediate casing section having a bottom opening therein so that a test specimen arranged below said bottom opening and exteriorly of said intermediate casing section is subject to said forwardly traveling blast wave, said intermediate casing section also having a top opening therein generally positioned above said bottom opening, and a generally wedge-shaped block arranged in the upper portion of said intermediate casing section and including a substantially horizontally extending rear edge and top and bottom faces forwardly diverging therefrom and a front end, the rear edge of said bl-ock being located adjacent to and lbelow the rear portion of said top opening and the front end of said block being located adjacent to the front portion of said top opening and rigidly secured to the adjacent upper wall portion of said intermediate casing section, whereby the top face of said block confronts said top opening and the bottom face of said block confronts said bottom opening, said block cooperating with said intermediate casing section to dene a passage from the upper portion thereof upwardly and forwardly over the top face of said block and through said top opening to the exterior, whereby said blast wave traveling forwardly through the air in said intermediate casing section exerts upwardly directed air pressure upon the bottom face of said block producing an upwardly directed force thereupon and also diverts air from the upper portion of said intermediate casing section at supersonic velocity through said passage to the atmosphere, whereby a shock wave becomes attached to the edge of said block and extends upwardly and forwardly therefrom through said top opening and over the t-op face of said block to the atmosphere, so that downwardly directed air pressure is developed below said shock wave upon the top face of said block, thereby to produce a downwardly directed force upon said block counterbalancing the upwardly directed force thereupon, with the result that no substantial unbalanced force is developed in said intermediate casing section incident to the forward travel of said- 14 blast wave therethrough and over said bottom opening.

13. The shock tube set forth in claim 12, and further comprising a container arranged below said bottom opening and adapted to contain the test specimen that is subject to said forwardly traveling blast wave, said container being supported in place below said bot-tom opening entirely independently of said intermediate casing section, so that forces exerted upon said container incident to the forward travel of said blast wave through said intermediate casing section and over said bottom opening are not transmitted from said container to said intermediate casing section.

14. The shock tube set forth in claim 12, wherein the top face of said block lies in a substantially at plane disposed at a small angle to the horizontal.

15. The shock tube set forth in claim 12, wherein the bottom face of said block is disposed in a first substantially horizontal plane and the top face of said block is disposed ina second plane extending upwardly and forwardly from the rear edge of said block and with said rst and second planes disposed at an angle of about 10 with respect to each other.

16. The shock tube set forth in claim 12, wherein said intermediate casing section is movable laterally between tan operative position placed between the respectively adjacent sends tof said rear and -front casing sections and an inspection position displaced from between the respectively adjacent ends of said rear and front casing sections, and further comprising mechanism operative to roll said intermediate section between said operative and inspection positions and to lpreserve the locations of longitudinal Iand circumferential zt of said intermediate casing section with respect to the adjacent ends of said rear and front casing sections when said intermediate casing section is returned into said operative position, whereby said bottom and top openings [always occupy respective bottom and ltop positions when said intermediate casing section is returned into said operative position.

17. The shock tube set forth in claim 16, wherein said mechanism essentially comprises a pair of substantially parallel longitudinally spaced-apart gears respectively carried by said intermediate casing section, and a pairv of substantially parallel longitudinally spaced-apart and laterally extending racks supported externally of said intermediate casing section and respectively engaging said gears.

18. A shock tube comprising an elongated substantially horizontally disposed tubular rear casing section, an elongated substantially horizontally disposed tubular front casing section, said rear and front casing sections being arranged in longitudinal alignment with each other and disposed in longitudinally spaced-apart relation, two elongated tubular intermediate casing sections, mechanism supporting said intermediate casing sections in substantially horizontally disposed side-by-.side relation for selective lateral movements between a common operative position and two individual inspection positions with respect t-o the adjacent ends of said rear and front casing sections, whereby either one of said intermediate casing sections m-ay be moved into said common operative position when the other of said intermediate casing sections occupies the one of said inspection positions individual thereto, each of said intermediate casing sections in said operative position -being arranged between the adjacent ends of said rear .and front casing sections and in longitudinal alignment therewith, each of said intermediate casing sections in the one of said inspection positions in dividual thereto being arranged from between the adjacent ends of said rear and front casing sections in laterally offset relation therewith, said rear and front casing sections and the one of said intermediate casing sections in said common operative position containing gaseous medium, means for producing a shock wave in the gaseous 15 16 medium contained in said rear casing section, said shock References Cited by the Examiner wave ybeing characterized by a substantial overpressure UNITED STATES PATENTS yand forward travel at supersonic velocity through the gaseous medium contained in said rear casing section and 218361063 5/1958 Yoler et al' 7?12 thence through the gaseous medium contained in said one 5 DAVID SCHONBERG, Primary Examiner. mtermediate casing sectlon and then through the gaseous medium contained in said front casing section, and a test S' FEINBERG RICHARD C' QUEISSER Exammers' station in said front casing section `and subject to Said LOUIS R. PRINCE, L. L. HALLACHER, forwardly traveling shock Wave. Assistant Examiners. 

1. A SHOCK TUBE COMPRISING AN ELONGATED TUBULAR CASING, A FRANGIBLE PARTITION CARRIED BY AN INTERMEDIATE PORTION OF SAID CASING AND INITIALLY DIVIDING SAID CASING INTO REAR AND FRONT CHAMBERS, SAID FRONT CHAMBER CONTAINING AIR, A FRANGIBLE DIAPHRAGM CARRIED BY THE REAR END OF SAID CASING AND INITIALLY CLOSING THE REAR END OF SAID REAR CHAMBER, MEANS FOR SUPPLYING A DETONABLE GAS INTO SAID REAR CHAMBER, MEANS FOR INITIATING DETONATION OF THE GAS IMMEDIATELY ADJACENT TO AND FORWARDLY OF SAID DIAPHRAGM SO THAT SAID DIAPHRAGM IS SUBSTANTIALLY INSTANTANEOUSLY RUPTURED BY THE DETONATION OF THE GAS TO PLACE THE REAR END OF SAID REAR CHAMBER INTO COMMUNICATION WITH THE ATMOSPHERE IN ORDER TO PREVENT SUBSTANTIAL RECOIL FORCES UPON SAID CASING, WHEREBY A DETONATION WAVE IS INITIATED IN THE GAS IN THE REAR END OF SAID REAR CHAMBER, SAID DETONATION WAVE BEING CHARACTERIZED BY A SUBSTANTIAL OVERPRESSURE AND FORWARD TRAVEL AT SUPERSONIC VELOCITY THROUGH THE GAS IN SAID REAR CHAMBER, MEANS RESPONSIVE TO SAID FORWARDLY TRAVELING DETONATION WAVE FOR SUBSTANTIALY EFFECTING RUPTURE OF SAID PARTITION AND THE CONSEQUENT PRODUCTION OF A BLAST WAVE IN THE AIR IN THE REAR END OF SAID FRONT CHAMBER, SAID BLAST WAVE BEING CHARACTERIZED BY A SUSSTANTIAL OVERPRESSURE AND FORWARD TRAVEL AT SUPERSONIC VELOCITY THROUGH THE AIR IN SAID FRONT CHAMBER, THE FRONT END OF SAID FRONT CHAMBER COMMUNICATING WITH THE ATMOSPHERE IN ORDER TO PREVENT SUBSTANTIAL THRUST FORCES UPON SAID CASING, AND AT TEST STATION IN SAID FRONT CHAMBER AND SUBJECT TO SAID FORWARDLY TRAVELING BLAST WAVE. 